Truss-frame for bridges



orrioii.

WILLIAM IfIOWE, OF 'WARREN MASSACHUSETTS.

TRUSS-FBAIVIE FCR BRIDGES.

To all whom t may concern Be it known that I, VJiLLiAM Howe, of Varren, in the county of Worcester and State of Massachusetts, have invented certain Improvements in. Truss-F rames, by means of` which improvements iny trussfraine can be so strained up as to give a tensile or stretching force longitudinally, and thus preventing that tendency to vibration which exists in truss-frames as ordinarily constructed, while at the sameftime a degree of camber may be given, which will raise the truss-frame in the center above a horizontal line.

This truss-frame, although intended for bridges, is applicable to roofs and various other structures; and I do hereby declare that the following is a full and exact description thereof.

Figure l, in the accompanying drawing is an elevation of a truss-frame; l, 1', are principal braces running in a direction from the abutments, or ends of the frame, toward the center, and 2, 2, are counter braces. The ends of these braces bear against pieces of wood or iron 6, 6, which are retained in place by being notched into the posts l0, v10, as shown in the drawing. The posts l0, l0, are double, that is to say, there is one on each side of the braces l and 2, said braces passing, and being embraced, between them where they cross each other at their center. Between the two end posts there is a piece of timber 3, 3, 3, which serves to cause the outer posts to bear their portion of the strain from tightening the braces, and to give them equal bearing 0n the string pieces. To give the required longitudinal strain to the trussframe, wedges, marked 4, 4, are inserted between each of the pairs of posts 10, 10, on each side of the truss frame, in a line with the upper and middle string pieces. To enable tnese wedges to act properly, and to prevent them from bruising the posts, I insert pieces of wood or metal 5, 5, between them and the said posts. The effect ofd-rivv ing the wedges, or keys, 4, 4, will be to foice the posts upon the ends of the braces; and as these wedges or keys are driven between the upper string pieces, they may be made not only to stiifen the truss frame, but to c'amber it to any desirable extent. Between t-he posts l0, 10, and against the lower string piece, I place blocks, or pieces, 7, 7, to afford proper bearing to the posts in that part; 8, 8, are the ends of the floor beams; 9, is

the lower string piece, 9 the middle, and 972 the upper string pieces. In this truss frame the upper and lower string pieces are treble, as shown at a, I), c, Fig. 2; the middle has two string pieces only, the braces cro-ssing between the posts, where, of course, there cannot be a string piece.

Fig. 2, is a plan of the braced floortinr bers, representing those on one side of a double track; l, is a horizontal brace, halved into the top of the iioor beams, o-r, if preferred, bolted on to them on their lower sides. 1When the track is single, the second brace 2, may be used. These braces are made to strain firmly against the posts of the truss frame by means of wedges or keys between their ends and the posts, as shown at CZ, el.

Fig. 3, is a portion of a truss frame having an arch-beam l, l, passing through the center of said truss. In this modification the posts 3, 3, are shown as made out of one piece of stuii, but slit down from the upper end so as to admit of the wedging up on the principle already described. The archbeam when used is to be cut olii' between the posts 3, 3, as shown in the segment Fig. A; the two ends of the beam, in the cut, should have a piece of iron or of hard wood interposed between them to prevent their galling. By the driving of the wedge 4, which bears against a shoulder in the posts, the trussframe will be raised, there being space left in the posts, below the arch beam, to admit of its being wedged down; 2, 2, are the braces and counter braces, operating as before described.

Fig. 4, represents another modiiication of the same principle, and differing only in arrangement from those described. The

post is shown as in a single piece, and slit down as in the last described arrange'- ment. In this the principal braces l, l, pass on the outside of the posts, to which they are pinned, or bolted, they being. also notched in, so that their lower and upper ends may bear in part against the posts, as well as upon-the pieces 6, 6, described in the first modification. The counter braces have their bearings between the posts.

Fig. 5, is a tbp,fi1i e3of-.Fig. 3, showing the string pieces and. the ends of the posts; and Fig. 6, is a similar view of Fig. 4.

Fig. 7, shows another modiiication of my truss-frame, having an arch beam, as in Fig. 3. In this the keys, or wedges, l, l, 1, are

driven betvveenthe principal and resisting braces; and itlvvill be seen. uponinspection that the same eect Will be produced, and that the principle of action is the same as in the other modifications. foregoing iigures represent the places of bolts, or dowels, through the timbers.

Having thus fully described the manner in which I construct my truss fram-e for bridges and similar structures, and shown various modes in Which I apply theV prin- Ciple upon Which I proceed in their formation, What I claim therein as Vconstituting my invention, and desire to secure by Letters Patent, is- Y l. The manner in Which I have combined and arranged the braces and counter braces, the double postsl` and the Wedges between them, as shoWnin Fig. l, so that by the driving of said Wedges the truss frame may be cambered in any desired degree, the Whole n tially as set forth.

The dots in the' being; constructed and operating vsubstani 2. I Claim `the `manner of carrying the same principle into effect by this combined operation `oi the Wedges, or keys, over the arch beam, and thosebetWeen the posts 8, 3,

' as shown in Fig. 3.

'8. I claim the applica-tion of the same principle by an arrangement ofbraces and counter braces, combined With an arch beam, the VWedges or keys `for combining being driven between the principal and resisting braces in the manner set forth, and represented in'Fig. 7, together with such `other modications `or variations of the same principle by'which the' same end may be attained by means substantially the same.

WILLIAM HOWE.

Witnesses:

JErTi-IAH BACON, DANmL HITCHCOCK." 

